#!/usr/bin/env python
# coding: utf-8

# 编写程序计算: 
# n=0：f(0) = 0
# n>0： f (n) = f (n - 1) + 100
# 
# 
# 输入：`n=5`
# 
# 预期输出：`500`
# 
# 

# In[1]:


def f(n):
    if n == 0:
        return 0
    return f(n - 1) + 100
n = 5
print(f(n))

